Demand for cellular phones is soaring, forcing makers of wireless equipment and network operators to invest billions to meet humanity's inexhaustible thirst for getting connected anywhere, anytime. Consumers expect their phones to deliver very clear voice signals and to pick up their e-mail, albeit slowly. But as frustrated callers know, communicating with mobile phones is tricky. Today's wireless networks use a maze of incompatible transmission standards, so users aren't guaranteed a dial tone when they travel. U.S. wireless operators alone use three competing standards, and just one of these is compatible with the leading standard in Europe, which itself has several variants. Most Asian wireless networks are built to another standard.
The wireless revolution's troubles go beyond conflicting standards. Consumers consistently expect more advanced features, e.g. Internet access. Worldwide, companies are spending billions to build a new network, usually referred to as “third generation,” or 3G, that is expected to bring broadband—detailed Web pages, music, even video—to your mobile phone. While exciting for consumers, these advances carry a price, since there's currently no easy way to upgrade mobile phones, or the base stations that carry their signals to the network, without changing hardware. Moreover, the wireless industry can't predict which offerings will be winners; the consequences of failing to guess right can be devastating.
The first cell phones relied on dozens of hardware components. In the past 15 years, programmable chips have been added, but their function is set immutably at manufacture. Today, dedicated, single-purpose chips do most of the work in mobile phone handsets and base stations; these chips are made as simple as possible to keep costs down. Given the conflicting standards and the uneven advent of the next generation of broadband wireless, manufacturers are starting to see dedicated components as a liability. A manufacturer that guesses wrong about the future standard will find itself with a lot of useless junk in its warehouses.
So more-general-purpose software that can be reprogrammed looks appealing. If mobile phones and their base stations were computers, new software could download easily through their wires. But wireless communication is fundamentally different. Mobile phones must push signals across the airwaves at precisely the right power level and in the exact transmission format. They must be tuned to receive incoming, powerful signals from one or more channels. Antennas catch irregular analog signals traveling through space on “carrier” frequencies; incoming radio signals must then be converted to an intermediate frequency through combination with another radio wave produced inside the receiver. Then the carrier wave gets subtracted to put the signal in baseband—that is, a power level and speed that ordinary digital processors can handle. While the signal is in baseband, it is translated into a stream of binary ones and zeroes, which are in turn decoded, decrypted and formatted into voice or data.
The first operations to benefit from reprogrammable software are operations in the baseband. In one model of Motorola base station, for example, the software that performs the baseband coding and decoding is reprogrammable.
Next, manufacturers would like reprogrammable software to handle the intermediate-frequency and radio-frequency parts of the job. That's a more difficult technological challenge, in part because silicon—which is by far the most common and least expensive chip material—does not handle radio-wave signals well. Radio-frequency processing of broadband signals will most likely use gallium arsenide chips running 100 billion instructions per second, compared to the roughly 10 to 100 million instructions per second in single-purpose chips in present-day phones.
The rise in computing complexity is exacerbated by the push to send signals much faster. So-called third-generation broadband wireless service could move data at two megabits per second, a roughly hundredfold leap from the operating speeds of most of today's wireless networks. All these demands mean chips will require lots more power; added power is far more easily obtained in a base station than in a small, lightweight mobile phone.
To start with, however, manufacturers are putting reprogrammable chips mainly into base stations that relay signals from cell phones to the network. Unlike handsets, base stations have few space or power constraints. For instance, Lucent Technologies, second to Motorola as a supplier of wireless base stations worldwide, has new models that are “smart” (that is, they have a flexibility endowed by software) at the antenna.
Cramming this kind of software-derived flexibility into lightweight handsets will not be easy. Even Mitola admits that “truly breakthrough technology” will be needed for a lightweight handset to flex among three or four frequency bands and operational modes. Meanwhile, smart, software-programmable wireless sets will find their way into vehicles, which can accommodate larger and heavier systems than people's pockets can. Indeed, one early use of flexible software radio technology will be in radios in police and fire vehicles: public safety agencies' wireless systems are notoriously incompatible. The FCC is encouraging public agencies to adopt this technology. Several firms, such as Vanu of Cambridge, Mass., are developing equipment for this market.
Wireless devices that morph through different “personalities” on the fly would be a boon to their users. But at the same time they create policy problems, as new technologies that cross boundaries often do. Historically, the FCC authorizes each piece of equipment for a type of use and specific channel. How should the regulators license mobile phones and base stations that can readily be changed after they're in use? How free should third parties be to load new software into your phone? How will it be possible to distinguish legitimate upgrades of the network from rogues trying subvert it?